From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C6A00C32789 for ; Tue, 6 Nov 2018 14:06:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 97AB82085B for ; Tue, 6 Nov 2018 14:06:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 97AB82085B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388581AbeKFXcE (ORCPT ); Tue, 6 Nov 2018 18:32:04 -0500 Received: from mx2.suse.de ([195.135.220.15]:37672 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2387928AbeKFXcE (ORCPT ); Tue, 6 Nov 2018 18:32:04 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id E1A37B67A; Tue, 6 Nov 2018 14:06:38 +0000 (UTC) Date: Tue, 6 Nov 2018 15:06:38 +0100 From: Michal Hocko To: Arun KS Cc: arunks.linux@gmail.com, akpm@linux-foundation.org, vbabka@suse.cz, osalvador@suse.de, linux-kernel@vger.kernel.org, linux-mm@kvack.org, getarunks@gmail.com Subject: Re: [PATCH v6 1/2] memory_hotplug: Free pages as higher order Message-ID: <20181106140638.GN27423@dhcp22.suse.cz> References: <1541484194-1493-1-git-send-email-arunks@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1541484194-1493-1-git-send-email-arunks@codeaurora.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 06-11-18 11:33:13, Arun KS wrote: > When free pages are done with higher order, time spend on > coalescing pages by buddy allocator can be reduced. With > section size of 256MB, hot add latency of a single section > shows improvement from 50-60 ms to less than 1 ms, hence > improving the hot add latency by 60%. Modify external > providers of online callback to align with the change. > > This patch modifies totalram_pages, zone->managed_pages and > totalhigh_pages outside managed_page_count_lock. A follow up > series will be send to convert these variable to atomic to > avoid readers potentially seeing a store tear. Is there any reason to rush this through rather than wait for counters conversion first? The patch as is looks good to me - modulo atomic counters of course. I cannot really judge whether existing updaters do really race in practice to take this riskless. The improvement is nice of course but this is a rare operation and 50ms vs 1ms is hardly noticeable. So I would rather wait for the preparatory work to settle. Btw. is there anything blocking that? It seems to be mostly automated. -- Michal Hocko SUSE Labs